Recoater system for additive manufacturing

ABSTRACT

Disclosed embodiments relate to recoater systems for use with additive manufacturing systems. A recoater assembly may be adjustable along multiple degrees of freedom relative to a build surface, which may allow for adjustment of a spacing between the recoater assembly and the build surface and/or an orientation of the recoater assembly relative to an orientation of the build surface. In some embodiments, the recoater assembly may be supported by four support columns extending above the build surface, and attachments between the recoater assembly and the support columns may be independently adjustable to adjust the recoater relative to the build surface.

RELATED APPLICATIONS

This Application claims the benefit of priority under 35 U.S.C. § 119(e)of U.S. Provisional Application Ser. No. 62/853,423, filed May 28, 2019,the disclosure of which is incorporated herein by reference in itsentirety.

FIELD

Disclosed embodiments are related to additive manufacturing recoatersystems and related methods.

BACKGROUND

Additive manufacturing systems employ various techniques to createthree-dimensional objects from two-dimensional layers. After a layer ofprecursor material is deposited onto a build surface, a portion of thelayer may be fused through exposure to one or more energy sources tocreate a desired two-dimensional geometry of solidified material withinthe layer. Next, the build surface may be indexed, and another layer ofprecursor material may be deposited. For example, in conventionalsystems, the build surface may be indexed downwardly by a distancecorresponding to a thickness of a layer. This process may be repeatedlayer-by-layer to fuse many two-dimensional layers into athree-dimensional object.

Some additive manufacturing systems may include a system for depositingand/or spreading a precursor material onto a build surface. For example,in powder bed fusion systems, a recoater assembly may be used to deposita layer of powder onto the build surface. A recoater assembly mayinclude a recoater blade connected to a recoater support structure,which may be controlled so as to drag the recoater blade across thebuild surface, smoothing the deposited powder to provide a layer ofuniform thickness.

SUMMARY

In one embodiment, a method of leveling a build surface of an additivemanufacturing system comprises detecting an orientation of a buildsurface, comparing the orientation of the build plate to a referenceorientation, depositing a layer of material having a non-uniformthickness onto a portion of the build surface, and fusing at least aportion the layer of material to form at least a portion of a buildsurface.

In another embodiment, a method of locating a contact point between arecoater blade and an obstacle on a build surface comprises translatinga recoater blade in a first orientation across a build surface in afirst pass and detecting a first contact point on the build surfacebased on a first contact between the recoater blade and an obstacle onthe build surface. The method further comprises translating the recoaterblade in a second orientation across the build surface in a second passdetecting a second contact point on the build surface based on a secondcontact between the recoater blade and the obstacle during the secondpass, and determining a position of the obstacle on the build surfacebased on the first contact point and the second contact point.

In a further embodiment, a method of operating a recoater of an additivemanufacturing system comprises obtaining a shape of a layer in anadditive manufacturing process, determining a portion of the shape ofthe layer having an edge parallel to a recoater blade when the recoaterblade is in a first orientation, displacing the recoater blade across aportion of the layer, and moving the recoater blade from the firstorientation to a second orientation prior to the recoater bladecontacting the edge. The recoater blade is not parallel to the edge whenthe recoater is in the second orientation.

It should be appreciated that the foregoing concepts, and additionalconcepts discussed below, may be arranged in any suitable combination,as the present disclosure is not limited in this respect. Further, otheradvantages and novel features of the present disclosure will becomeapparent from the following detailed description of various non-limitingembodiments when considered in conjunction with the accompanyingfigures.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures may be represented by a like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1 is a schematic perspective view of one embodiment of an additivemanufacturing system;

FIG. 2 is a schematic top view of the additive manufacturing system ofFIG. 1;

FIG. 3 is a schematic cross sectional front view of the additivemanufacturing system of FIG. 1;

FIG. 4 is a schematic side view of the additive manufacturing system ofFIG. 1;

FIG. 5A is a schematic side view of a build surface of an additivemanufacturing system in a level orientation, according to someembodiments;

FIG. 5B is a schematic side view of a build surface of an additivemanufacturing system in an out-of-level orientation, according to someembodiments;

FIG. 6 is a schematic top view of one embodiment of an additivemanufacturing system with recoater in an angled orientation;

FIG. 7 is a schematic top view of one embodiment an additivemanufacturing system configured to detect obstacles on a build surface;

FIG. 8 is a schematic top view of one embodiment an additivemanufacturing system illustrating dynamic adjustment of a recoaterorientation; and

FIG. 9 is a schematic cross sectional front view of one embodiment of anadditive manufacturing system including a recoater blade exchangesystem.

DETAILED DESCRIPTION

The inventors have recognized and appreciated numerous advantagesassociated with recoater assemblies that are movable and adjustablerelative to a fixed build surface in an additive manufacturing system.For example, such adjustability of the recoater assembly may facilitatealignment of the recoater. With any additive manufacturing systememploying a recoater to deposit layers of powder, there are at least twoimportant alignments. First, the recoater should be level across thewidth of the build surface. That is, the recoater itself should be levelalong its length with respect to the build surface. Second, the recoatershould be level along the length of the build surface. That is, therecoater should maintain a constant separation from the build surface asit moves relative to the build surface (e.g., along a directionperpendicular to the length of the recoater) to deposit a layer ofpowder. If the recoater is not well aligned in either of the two abovesenses, errors and/or defects may result. For example, a misalignedrecoater could result in deposited powder layers of non-uniformthicknesses, which may compromise the quality of a manufactured part.Additionally, a misaligned recoater may undesirably come into contactwith the build surface or powder bed, which could lead to damage to amanufactured part and/or damage to the additive manufacturing system.With layer thicknesses that may be on the order of only tens ofmicrometers, even slight misalignments may result in such errors and/ordamage. In conventional systems, in which support structures for therecoater are spatially fixed relative to the build surface, alignment istypically performed once during the initial setup of the additivemanufacturing system. Because precision alignment is needed to avoiderrors, the initial alignment of an additive manufacturing system maydictate a significant portion of the machine architecture. Yet,regardless of how well an initial alignment may have been performed,additional realignments may be required at later times, such as after anexchange of a recoater blade or upon beginning a new manufacturingprocess. Because the recoater support structures may be fixed relativeto the system in conventional architectures, these later realignmentsoften require substantial manual intervention, which may involveincreased demand on personnel as well as lost processing time.

In view of the above, the inventors have recognized and appreciatednumerous advantages associated with additive manufacturing systems thatinclude a recoater assembly that is movable along multiple degrees offreedom relative to a build surface. Compared to conventional recoatersystems that may only be translatable along a single direction parallelto a build surface, the recoater assemblies described herein may bemovable along multiple directions relative to a build surface. Asdescribed in more detail below, such movement of the recoater assemblymay facilitate various adjustments and alignments of the recoaterassembly to provide improved precision and reliability in an additivemanufacturing process, and may allow for the size of the additivemanufacturing system to be scaled up.

With respect to alignment of a recoater assembly, in some embodiments, arecoater assembly that is movable along multiple degrees of freedomrelative to a build surface may allow for fast and easy reorientation ofthe recoater to correct for any misalignments. For example, a recoaterassembly may be moveable along a first degree of freedom to correct fora misalignment of the recoater blade level across a width of a buildsurface, and the recoater blade assembly may be moveable along a seconddegree of freedom to correct for misalignment of the recoater along alength of the build surface. In this manner, many of the challengesdiscussed above regarding precision manual alignment of a fixed recoatersystem may be avoided. In some embodiments, such adjustment andrealignment of a recoater assembly may be automated. For example, anadditive manufacturing system may include one or more sensors to detectone or more alignments of the recoater, and the recoater assembly maymove along the multiple degrees of freedom in response to the sensorsdetecting that the recoater is misaligned.

With respect to increasing the scale of an additive manufacturingsystem, the inventors have recognized and appreciated that conventionalapproaches to additive manufacturing system design may not be wellsuited for larger scale systems, which may facilitate fabrication oflarger parts and/or parallel production of a larger number of partscompared to conventional smaller scale systems. For example, somechallenges may arise from an increase in the amount of powder requiredin larger systems, and correspondingly, an increase in the mass of thepowder supported on the build surface. As noted above, in a conventionaladditive manufacturing system, a build surface may move relative to therest of the system while a recoater assembly may remain verticallystationary. However, the inventors have recognized and appreciated thatin larger scale systems, it may be advantageous to employ a stationarybuild surface to avoid having to move a large powder mass by smallincrements corresponding to the layer thickness. For instance, moving abuild surface that supports a large mass may put undue stress on variouscomponents of the additive manufacturing system and may greatly reducethe system's achievable precision. Additionally, the mass of the powdersupported on the build surface may be variable throughout amanufacturing process as additional layers of powder are deposited ontothe build surface.

In view of the above, the inventors have recognized and appreciated thata recoater assembly that is movable along multiple degrees of freedomrelative to a build surface may advantageously facilitate verticalmovement of the recoater relative to a fixed build surface. In someembodiments, a recoater assembly may deposit a layer of material ontothe build surface, and subsequently the recoater may be indexed upwardlyabove the fixed build surface by a distance corresponding to the layerthickness. In this manner, the system may only be required to move thesmaller and constant mass of the recoater assembly to deposit the layersof powder in an additive manufacturing process, rather than moving thelarge and variable mass of the powder bed and build surface.

In addition to the above, the inventors have appreciated that a largerscale additive manufacturing system may require larger supportstructures to support the various components of the system, such as thebuild surface, recoater assembly, and/or optics assemblies. Relative tothe support structures in conventional smaller scale additivemanufacturing systems, these larger (e.g., longer) support structuresmay be prone to larger deflections, which may result in misalignmentbetween components of the additive manufacturing system, such as betweena recoater assembly and a powder bed, potentially resulting inmanufacturing errors or defects. Accordingly, some aspects describedherein may facilitate adjustment of the components of the system (e.g.,the recoater) to correct for such misalignments and/or support structuredeflection.

In some embodiments, an adjustable recoater assembly may include arecoater that is movable along support columns and support rails above abuild surface to facilitate adjustment of the recoater along multipledegrees of freedom. For example, in one embodiment, a recoater assemblymay include four support columns extending above the build surface, anda recoater may be supported on a pair of support rails extending betweenthe support columns. In particular, a first support rail may extendbetween first and second support columns and a second support rail mayextend between third and fourth support columns. The recoater may bemovable along the support rails to allow for movement of the recoaterblade along the length of the build surface to deposit a layer of powderonto the build surface. Additionally, each of the first and secondsupport rails may be coupled to the support columns via attachments thatare independently displaceable along the support columns. As describedin more detail below, displacing the attachments along the supportcolumns may allow for reorientation of the recoater relative to thebuild surface about at least two independent axes, which may facilitatealignment of the recoater relative to the build surface and/or tocorrect for misalignment resulting from deflection of one or moresupport structures. In particular, various support structures of arecoater system may exhibit non-negligible amounts of deflection(especially as the system size is scaled up to larger sizes) which maylead to varying spacing between the recoater and the build surface asthe recoater moves along support rails. For example, middle portions ofrecoater support rails supported near their ends may exhibit greaterdeflection relative to end portions of the support rails. Withindividual layer heights that may be on the order of tens of micrometersin an additive manufacturing process, such variable deflection cancorrespond to a substantial fraction of the layer height, which may leadto defects in a manufactured part. Accordingly, as discussed furtherbelow, some aspects described herein may allow for a recoater assemblyto dynamically adjust a spacing between the recoater and the buildsurface as the recoater moves along support rails to accommodate fordeflection of the support rails, thereby maintaining a constant layerthickness.

Moreover, the support rails and recoater may be vertically displacedalong the support columns to index the recoater to a new positioncorresponding to a subsequent powder layer in a manufacturing process.In this manner, the recoater assembly may be used in connection with anadditive manufacturing system having a fixed build surface (e.g., alarge scale additive manufacturing system).

In addition to the above, the inventors have recognized that in someadditive manufacturing systems, a build surface may be misaligned withinthe system such that the build surface is not level relative to a systemmaster level orientation, which may lead to errors, defects, and/ordamage as discussed above. According to some aspects, the adjustablerecoater assemblies described herein may facilitate leveling of a buildsurface prior to beginning an additive manufacturing process. Forexample, in some embodiments, an adjustable recoater assembly may beoperated to form one or more partial powder layers having non-uniformthicknesses in order to achieve a level build surface. After depositingeach partial layer, the partial layer may be at least partially fused.For example, the entire partial layer may be fused, or portions of thepartial layer may be fused, such as portions corresponding to anchorpoints in a subsequent manufacturing process. By depositing and fusingthe partial layers, portions of the build surface that are “low” (i.e.,farther from a point of reference above the build surface, such as arecoater or a laser system) may be brought closer to the remainder ofthe build surface. Of course, multiple partial layers may be depositedand fused in situations in which a build surface is significantly out oflevel and/or in which multiple, thinner partial layers are desired.

Another advantage of the adjustable recoater systems described herein isthat the recoater may be able to be moved over unused powder pilesduring an additive manufacturing process, which may allow for areduction of powder waste. In a conventional system, a recoater willoften be pushing excess, unused powder as it approaches the end of itstravel across a build surface. This unused powder will typically bepushed off of the build surface, and in many cases is discarded. Incontrast, the recoater assemblies described herein, which may be movablealong multiple degrees of freedom relative to a build surface may, atthe end of a pass, be moved away from the build surface to step over theunused powder, allowing the powder to be reused on the next pass,thereby reducing waste and lowering costs.

While certain advantages associated with a recoater assembly that ismovable in a direction perpendicular to a build surface (e.g.,vertically above the build surface) and rotatable about axes parallel toa plane of the build surface (e.g., to adjust the alignment of therecoater), the inventors have further recognized and appreciatedadvantages associated with a recoater that is rotatable about an axisperpendicular to the plane of the build surface. Accordingly, incontrast to conventional additive manufacturing systems in which arecoater is limited to travelling across a build surface in a directionperpendicular to the length of the recoater, the recoater systemdescribed herein may allow for the recoater to be moved across the buildsurface while the recoater blade is not perpendicular to the directionof movement of the recoater. In some embodiments, such adjustment of theangle of the recoater blade may be utilized to direct powder in adesired direction on the build surface. Typically, powder willpreferentially track in a direction perpendicular to the recoater blade.As such, a recoater that can be angled with respect to its direction ofmotion may be able to push powder in various directions as desired. Inthis manner, powder may be steered to desired portions of the buildsurface. For example, when forming a layer, certain regions of the layermay contain larger quantities of melted powder. Because powder mayshrink as it melts, these regions may consume more powder than otherregions. The recoater may compensate for this comparative deficiency inpowder by directing powder to such regions of high usage. Alternativelyor additionally, the recoater may be used to steer excess powder awayfrom regions of comparatively lower usage during an additivemanufacturing process.

In addition to the above, the inventors have appreciated thatadjustability of a recoater angle according to some embodimentsdescribed herein may provide numerous advantages related to detectionand/or avoidance of obstacles on the build surface. For example, in someinstances a recoater may encounter an obstacle during an additivemanufacturing process (e.g., a high point from a previous layer thatprotrudes into the current layer, or a contaminant) as it moves alongthe build surface. In a conventional system in which the angle of therecoater is constrained to be perpendicular to its direction of travel,a collision event with an obstacle may only inform an operator that anobstacle exists somewhere along a line defined by the recoater blade. Incontrast, the adjustable recoater systems described herein may allow anoperator to determine the specific location of an obstacle on the buildsurface. For example, in one embodiment, after detecting a firstposition of a collision with an obstacle on a first pass of therecoater, the recoater orientation may be adjusted to a new angle and asecond position of the collision with the obstacle may be detected in asecond pass. In this manner, the position of the obstacle may bedetermined based on the intersection of first and second linescorresponding to the orientations of the recoater blade at the first andsecond collision positions.

Additionally, the inventors have appreciated that being able to adjustthe angle of a recoater as it travels across a build surface may offeradvantages associated with avoiding certain interferences that may occurbetween the recoater and a manufactured part. Often, a layer of amanufactured part may contain one or more straight edges, and it may bedesirable to avoid parallel contact between a recoater blade and suchstraight edges. For example, parallel contact may cause the recoatersystem to jam, may damage the recoater blade, and/or may cause damage tothe part being manufactured. Although some parallel contacts may beavoided with thoughtful part layout on the build surface, some parallelcontacts may be inevitable in an additive manufacturing system with arecoater having a fixed orientation. In contrast, the adjustablerecoater systems described herein may be able to dynamically adjust anorientation of the recoater blade relative to an orientation of a partedge as it travels across the build surface, thus preventing and/oravoiding parallel contacts.

In addition to the above, some additive manufacturing systems, includingmany metal additive manufacturing systems, may utilize an enclosed buildvolume containing a process gas selected to maintain a desired gasenvironment around the build surface during an additive manufacturingprocess. For example, some systems may utilize inert gasses to avoidundesired oxidation of the powder and/or to limit impurities or otherundesirable processes. If a location within the build volume needs to beaccessed during an additive manufacturing process, such as if an one ormore components of the additive manufacturing system needs to beadjusted or replaced, the process gas may need to be purged from thebuild volume. In larger scale systems, which have correspondingly largerbuild volumes, such purging of the process gas may result incomparatively longer periods in which the additive manufacturing systemis out of service, as well as larger amounts of gas usage. The inventorshave appreciated that these increases in the time that the system is outof service, the time that an operator is occupied maintaining thesystem, and the larger volumes of gas consumed during purging allcontribute to higher costs and reduced efficiencies of the additivemanufacturing systems. Accordingly, as described in more detail below,some aspects described herein relate to systems for accessing theinterior of the build volume to perform adjustment and or replacement ofone or more components (e.g., replacement of a recoater blade) withoutrequiring purging of the entire build volume.

In some embodiments, an additive manufacturing system may include arecoater blade exchange system that is configured to allow a recoaterblade to be exchanged from a non-inert external environment (i.e., anopen manufacturing space exterior to an enclosed build volume) withoutrequiring the enclosed build volume to be purged. In some instances,exchange of a recoater blade may be desirable when the recoater bladebecomes damaged or otherwise due for replacement. For example, even ifnot damaged (e.g., by a collision with an obstacle), normal wear on arecoater blade may lead to inconsistencies in deposited layerthicknesses, and thus, it may be desirable to replace a recoater bladeat regular intervals (e.g., after a predetermined number of passes ofthe recoater), including one or more times during an additivemanufacturing process. In one embodiment, a recoater blade exchangesystem may include one or more valves in a build volume that mayinterface with various blade exchange chambers. A recoater may be movedwithin the build volume so as to be adjacent to a valve, at which pointthe recoater blade may be released and pulled into a blade exchangechamber through the valve. A new recoater blade may be transferred fromthe blade exchange chamber through a valve into the build volume, andthen attached to the recoater. In this manner, the recoater blade may bereplaced one or more times throughout an additive manufacturing processwithout requiring purging of the build volume and/or direct access tothe interior of the build volume, and thus disruptions of the additivemanufacturing process may be minimized.

Turning to the figures, specific non-limiting embodiments are describedin further detail. It should be understood that the various systems,components, features, and methods described relative to theseembodiments may be used either individually and/or in any desiredcombination as the disclosure is not limited to only the specificembodiments described herein.

FIGS. 1-4 are schematic representations of an additive manufacturingsystem 100, according to some embodiments. In the depicted embodiment,the additive manufacturing system 100 includes four support columns 102,two support rails 104, a recoater assembly including a recoater support110, a recoater blade housing 116, and recoater blade 118, as well as abuild surface 120. The four support columns and two support railssupport the recoater assembly at a desired height and orientation abovethe build surface, as discussed below.

Each support column 102 may be located near a corner of a build surface120, as may best be seen in FIGS. 1-2. For the sake of clarity, thebuild surface may be described as being contained within a planeparallel to an XY plane (i.e., a plane defined by an X axis and a Yaxis) shown in FIGS. 1-4. An X axis may be a direction parallel to alength of a build surface, while a Y axis may be a direction parallel toa width of a build surface. It should be understood that the currentdisclosure is not limited to any particular positions for the supportcolumns with respect to the build surface, e.g., in either the X or Ydirections. For example, the build surface 120 need not be containedwithin a perimeter defined by the four support columns, as shown inFIGS. 1-4. In some embodiments, portions of the build surface 120 mayextend beyond one or more support columns 102. Moreover, while a systemincluding four support columns 102 is shown in FIGS. 1-4, it should beunderstood that other configurations may be suitable. For example, someembodiments may include more than four support columns.

For the sake of clarity, each of four support columns 102 may beindividually identified. Without loss of generality, a first supportcolumn 102 a may be a support column nearest to an origin of acoordinate system, as shown in FIGS. 1-4. A second support column 102 bmay be located at a first distance from the first support column alongan axis parallel to the X axis. A third support column 102 c may belocated at a second distance from the first support column along an axisparallel to the Y axis. A fourth support column 102 d may be located ata first distance from the first support column along an axis parallel tothe X axis and at a second distance from the first support column alongan axis parallel to the Y axis. Each support column may extend in avertical direction. As used herein, the term “vertical” may refer to adirection that is substantially parallel to a Z axis, wherein the Z axismay be defined as being perpendicular to a reference plane which may,for example, include a build surface 120 that is level. In this manner,the support columns 102 may extend vertically above the build surface120.

The system 100 further includes two support rails 104 be connected tothe four support columns 102. In particular, each of the two supportrails is connected to two of the four support columns 102. A length ofeach support rail may be along an axis parallel to the X axis, as shownin FIGS. 1-4. In the depicted embodiment, a first support rail 104 a isconnected to the first support column 102 a and the second supportcolumn 102 b, and a second support rail 104 b is connected to the thirdsupport column 102 c and the fourth support column 102 d.

Coupling between the support rails 104 and the support columns 102 isachieved via translational attachments 106 and rotational attachments108. In particular, the first support rail 104 a is coupled to the firstsupport column 102 a via a first translational attachment 106 a and afirst rotational attachment 108 a. The first support rail 104 a is alsocoupled to the second support column 102 b via a second translationalattachment 106 b and a second rotational attachment 108 b. Similarly,the second support rail 104 b is coupled to the third support column 102c and the fourth column 102 d via third and fourth translationalattachments 106 c and 106 d, respectively, as well as third and fourthrotational attachments 108 c and 108 d, respectively.

The various translational attachments 106 may allow ends of each supportrail 104 to translate vertically (i.e., in a direction parallel to the Zaxis) along the support columns 102. The rotational attachments 108 mayallow the support rails 104 to rotate about connection points betweeneach support rail and a corresponding support column 102 to which thesupport rail is attached. For example, referring to FIG. 4, the firstrotational attachment 108 a may allow the first support rail 104 a torotate about a connection point between the first support rail 104 a andthe first support column 102 a. In this embodiment, such rotation isabout an axis parallel to the Y axis.

In some instances, if two ends of a support rail 104 translate an equaldistance along corresponding support columns, the support rail maytranslate vertically and an orientation of the support rail may notchange. In other instances, if the two ends of the support rail 104translate by different distances along the corresponding supportcolumns, an orientation of the support rail may change. This change oforientation may be facilitated by the rotational attachments 108.Moreover, in some embodiments in which a support rail may changeorientation, the support rail may be configured to extend and/or retractto accommodate a variable distance between attachments between thesupport rail and support columns.

As noted above, the recoater assembly includes a recoater support 110, arecoater blade housing 116, and a recoater blade 118. The recoater bladehousing 116 may be configured to securely hold the recoater blade, andmay be mounted to the recoater support. The recoater support 110 may becoupled to the support rails 104. In the depicted embodiment, therecoater support 100 extends between the support rails 104 along an axisparallel to the Y axis, as shown in FIG. 1. In particular, the recoaterrail 110 is coupled to the first support rail 104 a via a first recoatertranslational attachment 112 a and a first recoater rotationalattachment 114 a. Similarly, the recoater support 110 is coupled to thesecond support rail 104 b via a second recoater translational attachment112 b and a second recoater rotational attachment 114 b.

The recoater translational attachments 112 may allow ends of therecoater support 110 to translate horizontally relative to the buildsurface (i.e., in a direction parallel to the X axis, as shown inFIG. 1) along the support rails 104. The recoater rotational attachments114 may allow the recoater support 110 to rotate about connection pointsbetween the recoater support and support rails 104. For example,referring to FIG. 2, the first recoater rotational attachment 114 a mayallow the recoater support 110 to rotate about a connection pointbetween the recoater support 110 and the first support rail 104 a. Insome embodiments, such rotation may be about an axis parallel to the Zaxis. In some embodiments, the rotation may alternatively oradditionally be about an axis parallel to the X axis. That is, therecoater rotational attachments 114 may enable rotation about at leasttwo axes (i.e., axes parallel to the X and Z axes, as shown in FIG. 1).

In some applications, repositioning of the various translationalattachments described herein may result in different positions andorientations for the recoater assembly. For example, equal translationof four translational attachments 106 may cause the recoater totranslate vertically without changing orientation relative to the buildsurface 120. Differential translation of pairs of translationalattachments 106 may reorient the recoater relative to the build surface.For example, translating the first translational attachment 106 a andsecond translational attachment 106 b a first distance that is differentthan a second distance translated by the third translational attachment102 c and fourth translational attachment 106 d may “roll” the recoater(i.e., cause the recoater to rotate about an axis parallel to the Xaxis). Similarly, translating the first translational attachment 106 aand the third translational attachment 106 c differently than the secondtranslational attachment 106 b and the fourth translational attachment106 d may “pitch” the recoater (i.e., cause the recoater to rotate aboutan axis parallel to the Y axis). Similarly, repositioning of therecoater translational attachments may result in different positions andorientations for the recoater assembly. For example, equal translationof two recoater translational attachments 112 may cause the recoater totranslate horizontally (i.e., in a direction parallel to an X axis)without changing orientation. Differential translation of recoatertranslational attachments may reorient the recoater assembly within aplane defined by the translational attachments 106. That is, translatinga first recoater translational attachment 112 a differently than asecond translational attachment 112 b may “yaw” the recoater (i.e.,cause the recoater to rotate about an axis parallel to a Z axis). Ofcourse, it should be understood that various combinations of such roll,pitch, and yaw adjustments may be used to achieve a desired orientationfor the recoater assembly relative to the build surface.

It should be appreciated that some rotations or other adjustments of arecoater assembly may result in a change in an effective length of therecoater assembly (depicted as “L” in FIG. 2). For example, when therecoater assembly yaws, a distance between attachments on two supportrails may change. Similarly, when the recoater rolls, a distance betweenthe two support rails change may change. Accordingly, in someembodiments, the recoater assembly may be configured to adjust itslength L to accommodate these changes in distance between attachmentsand/or support rails. For example, the translational attachments 114and/or rotational attachments 116 may include extendable linkages (notdepicted) or other suitable structures to accommodate such extension.Alternatively or additionally the recoater support 110 may be extendable(e.g., via a telescopic configuration) to accommodate such changes inlength of the recoater assembly.

Depending on the particular embodiment, it may be desirable toreposition and/or reorient a recoater for a variety reasons. Forexample, the recoater assembly may be translated in the X direction touniformly spread powder over the build surface 120 in preparation forpatterning by exposure to an energy source, such as one or more laserenergy sources. Translation of the recoater in the X direction may beaccomplished, for example, by translating the first and second recoatertranslational attachment 112 a and 112 b a desired distance along thefirst and second support rails 104 a and 104 b, respectively.

In addition, the recoater assembly may be repositioned verticallyrelative to the build surface after depositing a layer of material onthe build surface (e.g., during intervals between patterning layers in amanufacturing process) in order to index the recoater assembly to aposition corresponding to subsequent layers of the manufacturingprocess. As discussed previously, in some additive manufacturingsystems, a build surface may be indexed downwardly with respect to arecoater a distance equal to a desired layer height. However, there maybe certain disadvantages associated with moving a build surface, asdiscussed above. Accordingly, the systems described herein allow therecoater to be indexed upwardly with respect to the build surface, whichmay remain fixed in position throughout the manufacturing process. Thisindexing may correspond to translation of the recoater in the Zdirection, which may be accomplished by the translating fourtranslational attachments 106 a distance along respective supportcolumns 102 (e.g., a distance corresponding to the layer thickness).

Depending on the particular embodiment, a distance between a recoaterand a build surface may be measured and/or controlled via any suitabletypes of measurement or control systems. For example, vertical motion ofa recoater assembly (e.g., along support columns 102) may be driven bymotion stages such as ball screw driven stages, linear motor stages,linear actuators, pneumatic actuators, hydraulic actuators, and so on.Moreover, the position of such vertical motion stages may be trackedand/or measured via systems such as rotary encoders on ball screws,linear optical encoders, LVDT sensors, laser displacement sensors, andso on. For example, in one embodiment, a vertical motion stage may bedriven by a ball screw driven linear actuator, and the position of themotion stage may be tracked via linear optical encoders. Of course, itshould be appreciated that the current disclosure is not limited to anyparticular combination of types of vertical motion stages and/or systemsfor tracking or measuring the position of the motion vertical motionstages. Similarly, the systems disclosed herein may include any suitabletypes of motion stages for accommodating movement of the recoaterassembly along the support rails 104. For example, the recoater assemblymay be driven along the support rails via ball screw driven linearslides, belt driven linear actuators, pneumatic actuators, hydraulicactuators, and so on, and the position of the recoater assembly may bemonitored via one or more of rotary encoders, linear optical encoders,LVDT sensors, laser displacement sensors, and so on.

As discussed above, the adjustable recoater assemblies described hereinmay advantageously allow for the recoater assembly to be adjusted toachieve a desired alignment of the recoater assembly. For example,differential displacement of the various attachments may enablereorientation of a recoater about various axes. In some instances, theability to reorient a recoater about axes parallel to a build surfacemay obviate the need for precision alignment of the recoater duringinitial setup of the additive manufacturing system. Furthermore, laterrealignments of the recoater may be performed automatically withoutoperator intervention, which may reduce the time that the additivemanufacturing system is inoperable for maintenance. It should beappreciated that such benefits of the adjustable recoater assembliesdescribed herein in connection to alignment between the recoater and abuild surface may be applicable to additive manufacturing systems witheither a fixed build surface or a movable build surface.

In some embodiments, an additive manufacturing system may include one ormore sensors and actuators that may be used to at least partiallyautomate an alignment process of a recoater assembly. For example, thesystem 100 of FIG. 1 includes a first sensor 152 configured to detect anorientation of the build surface 120, and a second sensor 154 configuredto detect an orientation of the recoater assembly. If a recoater isdetermined to be out of alignment with the build surface (e.g., based onan orientation measured by the sensors 152 and 154), the recoater may bereoriented to be brought into alignment with the build surface. Each ofthe sensors 152 and 154 is operatively coupled to a controller 150,which may determine a suitable adjustment to bring the recoater assemblyand the build surface into alignment. For example, the controller 150may determine an adjustment to the recoater assembly such that therecoater assembly is parallel to the build surface after the adjustment.Moreover, the controller 150 may be operatively coupled to one or moreactuators associated with one or more of the attachments 106, 108, 112and/or 114, and the controller may control operation of each actuator tomove the recoater assembly and achieve a desired adjustment. Dependingon the particular embodiment, the one or more sensors may includecontact probes, laser displacement sensors, accelerometers, gyroscopes,and/or or any other suitable type of sensor, as the disclosure is notlimited in this regard.

As discussed previously, various support structures of an additivemanufacturing system may exhibit non-negligible amounts of deflection.For example, referring to FIGS. 1 and 4, the first support rail 104 amay be supported only at its two ends. As such, the first support railmay experience deflection in a vertical direction (i.e., along the Zaxis), due in part to the weight of the first support rail itself, aswell as in part to the weight of the recoater assembly that the firstsupport rail supports. With layer heights that may be on the order oftens of micrometers, even minimal deflection of a support structure inan additive manufacturing system may be consequential. As may beappreciated by a person of skill in the art, an amount of deflection ofa support rail 104 may vary as a function of position along a length ofthe support rail. Specifically, the deflection of a support rail may belesser at points closer to support columns 102 and may be greater atpoints closer to a center of the support rail. Consequently, a heightabove a build surface 120 of a portion of a support rail 104 may vary asa function of length along the support rail. Accordingly, in someembodiments, an additive manufacturing system may compensate for suchheight variations of the support rail by moving both ends of the supportrail as a recoater travels along the support rail in order to maintain aconstant layer thickness throughout a manufacturing process,

For example, referring to FIG. 4, a recoater may initially be positionednear the first support column 102 a at a first height above a buildsurface 120, and may be configured to translate toward the secondsupport column 102 b along the first support rail 104 a. As the recoatertranslates away from the first support column, the recoater may be at aposition along the first support rail at a second height above the buildsurface. As explained above, the second height may be less than thefirst height due to a deflection of the first support rail. Tocompensate for a difference between the first height and the secondheight, the first translational attachment 106 a and the secondtranslational attachment 106 b may translate upwardly, moving the firstsupport rail 104 a vertically away from the build surface 120 a distancethat may be equal to the difference between the first and secondheights. Similarly, the third translational attachment 106 c and fourthtranslational attachment 106 d may also translate upwardly, moving thesecond support rail 104 b vertically the same distance, in order to keepthe recoater from rotating about an axis parallel to an X axis (i.e., toprevent rolling the recoater). Of course, such a process may occurcontinuously as the recoater translates along the support rails,allowing the recoater to maintain a constant height above the buildsurface, thus enabling a layer of constant thickness. Moreover in someembodiments, an additive manufacturing system may include one or moresensors configured to dynamically measure a distance between therecoater assembly and the build surface 120 as the recoater moves alongthe build surface. The additive manufacturing system may be configuredto automatically adjust the vertical position of the recoater assemblyalong the support columns to maintain a constant distance between therecoater assembly and the build surface for each layer deposited by therecoater.

The inventors have recognized and appreciated that in some instances, abuild surface of an additive manufacturing system may become out oflevel with respect to a master reference level of the additivemanufacturing system. As discussed above, some embodiments of additivemanufacturing systems may include one or more sensors configured todetect an orientation of a build surface. If the sensors detect that thebuild surface is misaligned with respect to a recoater assembly, onestrategy to compensate for such misalignment may be to reorient therecoater by adjusting the various attachments between rails and columnsas discussed above. In addition to this strategy, recoater assembliesthat are movable and adjustable relative to a build surface in anadditive manufacturing system may also be used to accommodate amisaligned build surface by leveling the build surface, as discussedbelow in connection with FIGS. 5A-5B.

FIG. 5A shows a build surface 220 with a first layer of material (e.g.,powder) 222 a deposited on the build surface. In FIG. 5A, the buildsurface 220 is aligned relative to a recoater and master referenceorientation of an additive manufacturing system, as shown by theorientation of the Z axis being perpendicular to the build surface. Insituations in which a build surface is aligned with respect to arecoater, such as in FIG. 5A, no adjustment to the level of the buildsurface may be needed.

In contrast, FIG. 5B shows a build surface 220 with multiple layers 222.It should be appreciated that the build surface in this figure ismisaligned with respect to a recoater and the master referenceorientation of the system, as illustrated by the angle formed betweenthe Z axis and the build surface. In such situations in which the buildsurface is misaligned with respect to the recoater and master referenceorientation of the system, such as in FIG. 5B, the build surface may beleveled by depositing one or more partial layers, as detailed below.

A partial layer may be a layer 222 of precursor material (e.g., powder)that may not cover an entirety of the build surface 220. Partial layersmay be achieved by depositing powder during only a portion of the timethat a recoater is moving across the build surface. That is, therecoater assembly may stop depositing powder before the recoaterfinishes moving across the build surface, thus only depositing powderover a portion of the build surface. Once a partial layer is deposited,a portion and/or the entirety of the partial layer may be fused,allowing additional partial layers (or full layers) to be deposited asdesired.

Referring to FIG. 5B, a first layer 222 a deposited on a misalignedbuild surface 220 may be a partial layer. The first layer 222 a may bedeposited such that its top surface is aligned with respect to arecoater assembly (as suggested in FIG. 5B by the parallel relationshipbetween the top surface of the first layer 222 a and the X axis). Afterat least a portion of the first layer 222 a is fused, a second layer 222b may be deposited. Because the first layer 222 a may be a partiallayer, the second layer 222 b may be deposited in part on the firstlayer 222 a and in part on the build surface 220. Again, at least aportion of the second layer may be fused, upon which a third layer 222 cmay be deposited. After fusing at least a portion of the third layer, afourth layer 222 d may be deposited. In the example shown in FIG. 5B,the fourth layer 222 d covers the area of the entire build surface 220.Consequently, depositing and selectively fusing layer 222 d may fullylevel the build surface, preparing it for a manufacturing process. Whilethree partial layers 222 a-222 c are shown in FIG. 5B, it should beunderstood that the current disclosure is not limited to any particularnumber of partial layers used in connection with achieving a level buildsurface. For example, other embodiments may employ fewer than threepartial layers, or more than three partial layers.

In some embodiments, a partial layer may include portions having asubstantially uniform thickness, as well as portions having a variablethickness. For example, referring to FIG. 5B the third layer 222 c maybe substantially a uniform thickness for a majority of the layer thatoverlies layer 222 b, but in a portion of layer 222 c that is in directcontact with a build surface 220, the layer may begin to taper, yieldinga variable thickness for a portion of the layer.

It should be appreciated that an entire partial layer need not be fusedor otherwise solidified in order to level a build surface. In somecases, only portions of a partial layer may be fused. For example, onlythe portions of a partial layer that may be used to support amanufactured part, such as anchor points, may be fused. Selectivelyfusing one or more partial layers may enable a faster build plateleveling process and may limit powder waste.

FIG. 6 shows a top schematic view of one embodiment of an additivemanufacturing system 300 including an angled recoater assembly. Asdiscussed above, a recoater may be reoriented about a Z axis (i.e., a“yaw” orientation) by adjusting attachment points between a recoatersupport and support rails, such as by controlling positions of recoatertranslational attachments 312. In some embodiments, one of a firstrecoater translational attachment 312 a and a second recoatertranslational attachment 312 b may be actuated, and the other may bepassive. In some embodiments, both the first and second recoatertranslational attachments may be actuated. In embodiments in which boththe first and second recoater translational attachments are actuated, asingle actuator may be coupled to both attachments, or a dedicatedactuator may be associated with each attachment and the dedicatedactuators may be coupled through a controller.

The inventors have appreciated multiple advantages associated with arecoater assembly that is able to yaw in this manner. For example, sucha recoater assembly may be capable of pushing powder in a desireddirection. As would be understood by a person of skill in the art,powder may preferentially track in a direction perpendicular to a lengthof a recoater blade. In a conventional additive manufacturing system inwhich an orientation of a recoater may be constrained, powder may onlybe able to be pushed in a single direction, which may be a direction oftravel of a recoater. In additive manufacturing systems with a recoaterthat may yaw, reorienting a recoater may change a direction in whichpowder may be pushed by a recoater blade. As shown in FIG. 6, a recoaterthat is yawed may push powder in a direction D that is distinct from adirection of travel of a recoater (which, in this example, may be adirection parallel to the X axis). In some instances, the direction D inwhich powder is pushed be adjusted dynamically throughout amanufacturing process and/or during a single recoating step to deposit alayer of material onto a build surface. The ability to direct powder todifferent portions of the build surface may be advantageous tocompensate for areas of high powder usage and/or to direct excess powderaway from areas of lower powder usage. For example, as powder is meltedand solidified to form portions of a manufactured part, the powder mayshrink; consequently, portions of a build surface that contain many partfeatures may use more powder than other portions of the build surface.The ability to direct powder may be useful to refill these areas of highpowder usage.

In addition to directing powder, the ability to yaw a recoater asdiscussed above may be used in connection with detecting obstacleslocated on a build surface. For example, an obstacle may include a highpoint from a previous layer, a contaminant, or any other physical objectthat may impede the motion of the recoater assembly. In someembodiments, a method of detecting an obstacle may include moving arecoater across a build surface in different orientations. As therecoater makes contact with obstacle in these different orientations,the location of the obstacle may be determined as discussed below inconnection with FIG. 7.

FIG. 7 illustrates one example of a method for detecting an obstacle ona build surface. First, a recoater may be moved across the build surface420 in a first orientation O₁. When the recoater blade makes contactwith an obstacle 424, positions of the ends of the recoater assembly maybe recorded. For example, the positions of the ends of the recoater maybe recorded with one or more encoders, displacement sensors, or bymonitoring the current delivered to motors that may move the recoater.Of course, other sensors or mechanisms may be used to record a positionof an end of a recoater, and the disclosure is not limited in thisregard. With the positions of the two ends of the recoater recorded, afirst line across the build surface may be defined. The recoaterassembly may subsequently be yawed to a second orientation O₂. Afteryawing the recoater to this second orientation, the process may berepeated, thus defining a second line across the build surface. Alocation of the obstacle 424 may be determined based on an intersectionof the first and second lines.

In addition to the above, the ability to yaw a recoater may have furtherbenefits associated with avoiding damaging a manufactured part and/or arecoater blade as the recoater blade is moved across a build surface todeposit a layer of material. The inventors have appreciated that it maybe desirable to avoid a parallel contact between a recoater blade and astraight edge of a manufactured part formed in a prior layer of amanufacturing process (i.e., a previously printed layer). Rather, it maybe preferable to approach a straight edge of a manufactured part withthe recoater blade at an angle with respect to such part edges. Althoughstrategic part orientation may mitigate some parallel contacts, otherparallel contacts may be unavoidable. For example, some parts mayinclude a straight edge that rotates as a function of height, which maygreatly increase the chances that at least one layer may contain astraight edge that may be parallel to an orientation of a recoaterblade. A recoater assembly that is able to change orientation may beable to avoid parallel edge contacts regardless of part orientation.

Referring to FIG. 8, a particular layer in a manufacturing process maycontain multiple straight-edge obstacles 526. A recoater may initiallybe in a first configuration in which a length of the recoater isparallel to a Y axis. If the recoater were to travel across a buildsurface 520 in this first configuration, a recoater blade may make aparallel contact with a first straight-edge obstacle 526 a. However, ifthe recoater yaws into a first orientation O_(a) prior to reaching thefirst straight-edge obstacle, as shown in FIG. 8, a parallel contact maybe avoided. After moving past the first straight-edge obstacle, therecoater may approach a second straight-edge obstacle 526 b. Similarly,if the recoater were to continue travelling in the first orientationO_(a), the recoater blade may make a parallel contact with the secondstraight-edge obstacle 526 b. However, the recoater may yaw into asecond orientation O_(b) in order to avoid such a parallel contact.Finally, before reaching a third straight-edge obstacle 526 c, therecoater may again yaw into a third orientation O_(c) in order to avoida parallel contact that may have occurred had the recoater remained inthe second orientation O_(b) upon reaching the third straight-edgeobstacle 526 c. As stated above, it should be understood that yawing ofthe recoater may be accomplished dynamically as the recoater movesacross the build surface, and the recoater assembly need not stop inorder to yaw. In this manner, the recoater assembly may be adjusted toavoid parallel contact with any suitable number of edges in a partduring an additive manufacturing process.

In some instances, a recoater blade of an additive manufacturing systemmay become damaged (e.g., due to contacts with obstacles and/or vianormal wear on the recoater blade). For example, repeated contacts overtime between the recoater blade and powder, part edges, or obstacles maycause cuts and/or grooves to form in the recoater blade. These cutsand/or grooves may undesirably leave tracks in layers of powder, whichmay in turn cause voids and/or inclusions in manufactured parts, whichmay compromise the quality of manufactured parts. In some instances,recoater blade quality may be determined by capturing images after eachlayer of a manufacturing process and automatically scanning the capturedimages for discrepancies between the captured images and predicted layerimages (from, for example, a CAD/CAM program). In other instances,damage to a recoater blade may be detected by scanning or imaging alayer of powder after it has been deposited by the recoater but beforeany fusion of the layer has occurred. For example, damage to therecoater blade may be detected as lines, divots, or other defects inwhat should otherwise be a smooth powder surface.

Depending on the particular embodiment, a recoater blade may be made outof any suitable types of materials, such as metal, ceramic, plastic,and/or rubber. However, regardless of the particular type of materialused for the recoater blade, the blade may become damaged during use,including during an additive manufacturing process. In some instances, atime period over which a recoater blade is useable (which may bedetermined based on a number of coating passes that can be made with aparticular recoater blade) may be less than a time period associatedwith a single additive manufacturing process. For example, a singleadditive manufacturing process may involve a number of layers that islarger than the number of passes that can be performed with a singlerecoater blade. Consequently, a recoater blade may need to be replacedduring the course of a manufacturing process.

In conventional additive manufacturing systems, recoater bladereplacement may be performed manually by an operator. Such replacementsmay be slow, requiring sufficient time to allow a manufactured part tocool, which may alter the thermal history of the part and potentiallyaffect build quality. Of course, such manual intervention also requiresactive participation of an operator, preventing the operator fromperforming some other useful task. Additionally, as discussed above,manual replacement of a recoater blade may require purging a buildvolume to permit access to a recoater assembly located within the buildvolume, which may both be time intensive and result in wasted processgas.

In some conventional additive manufacturing systems, an automated systemmay be included within the build volume to enable automatic exchange ofthe recoater blade. Additional blades may be pre-loaded into the buildvolume such that an automated mechanism may be able to exchange one ormore blades automatically. However, the inventors have recognizednumerous disadvantages associated with such systems. For example, thesesystems require that a sufficient number of blades be loaded for a givenmanufacturing process. As the size of a build volumes increases, thenumber of printed layers to complete a full process may start toapproach 10,000 or more layers. Being able to predict and support enoughspare blades to enable sufficient blade exchange to support somemanufacturing processes may require an internal exchange and storagemechanism that is too large, and/or too expensive to be practical. Incontrast, the systems and methods described herein may allow a new bladeto be introduced from an external environment (e.g., manufacturing spacehaving a non-inert gas environment) into a gas-tight build volumewithout contamination of an inert gas environment within the buildvolume. This exchange may be performed an unlimited number of times fora given manufacturing process, and the size and cost of the system maybe substantially less compared to conventional approaches.

The inventors have appreciated that an additive manufacturing systemincluding a recoater blade exchange system that requires minimalinterruption to a manufacturing process and that permits exchange ofblades between an exterior of an enclosed build volume and an interiorof the build volume may address many of the above-mentioned shortcomingsof conventional additive manufacturing systems. FIG. 9 shows oneembodiment of a recoater blade exchange system for an additivemanufacturing system 600. Similar to the embodiments described above,the system includes a recoater assembly including a recoater support610, a recoater blade housing 616, and a recoater blade 618.

When replacement of the recoater blade 618 is desired (e.g., if therecoater blade becomes damaged), the recoater assembly may be moved to arecoater blade exchange position within the build chamber 628 tofacilitate exchange of the recoater blade. In particular, the system 600includes a recoater blade exchange chamber 632 mounted to the buildchamber 628 at a position associated with the recoater blade exchangeposition. Once in the recoater blade exchange position, the recoaterblade housing 616 may be detached from the recoater support 610. Arecoater blade gripper 634 may be at least partially received into thebuild chamber through a valve 630 to engage the recoater blade housing616. Subsequently, the recoater blade gripper may pull the recoaterblade housing 616 (and the recoater blade 618) out of the build chamberand into the recoater blade exchange chamber 632. In some embodiments, anew recoater blade housing and recoater blade may then be inserted intothe build chamber with the recoater blade gripper and attached to therecoater support. In other embodiments, the recoater blade may beremoved from the blade housing after being removed from the buildchamber, and a replacement blade may be attached to the recoater bladehousing. The housing and replacement blade may be reinserted into thebuild chamber and attached to the recoater support via the gripper, asdiscussed above.

In some embodiments, assemblies of recoater blades and recoater bladehousings may be prepared and stored for subsequent use so that aplurality of such assemblies may be available during an additivemanufacturing process. Depending on the embodiment, extra assemblies maybe stored within a build chamber 628, in a recoater blade exchangechamber 632, or external to an additive manufacturing system 600. Insome embodiments, an additive manufacturing system may include multiplerecoater blade exchange chambers. For example, a used and/or damagedrecoater blade may be removed into a first blade exchange chamber, andsubsequently, the recoater may be moved into alignment with a secondblade exchange chamber containing a replacement blade, and thereplacement blade (and blade housing) may be attached to the recoatersupport. The used and/or damaged blade may later be removed from thefirst chamber, and a new blade may be prepared and loaded into the firstchamber for subsequent replacement operations.

In the depicted embodiment, the recoater blade exchange chamber 632 iscoupled to the build chamber 628 through a valve 630. For example, thevalve may be an isolation valve, such as a ball valve. The valve may bemovable between a closed position, in which the build chamber 628 isisolated from an outside environment, and an open position in which thevalve may allow access into the build chamber through the valve. In someembodiments, the recoater blade exchange system may include a singlevalve through which used and/or damaged recoater blade assemblies may beremoved, and through which new recoater blade assemblies may beinserted. In other embodiments, two or more valves may be included. Forexample, a first valve may be used for removal of used recoater bladeassemblies, and a second valve may be used for insertion and attachmentof replacement recoater blade assemblies. In embodiments with two ormore valves, an additive manufacturing system 600 may include multiplerecoater blade exchange chambers 632, multiple recoater blade exchangepositions, and/or multiple recoater blade grippers 634.

Referring again to FIG. 6, the system 600 includes a seal 636 positionedat an end of the recoater blade exchange chamber 632 opposite the valve630. The seal may allow a portion of a recoater blade gripper 634 toextend outside of a recoater blade exchange chamber 632, for example, tobe manipulated by an operator. The seal may avoid or prevent gasexchange between the interior build chamber 628 and an externalenvironment when the valve 630 is in the open position. Depending on theembodiment, the seal may be a spring loaded lip seal, a labyrinth seal,or any other suitable type of seal, as the disclosure is not limited inthis regard.

As noted above, the recoater blade gripper 634 may be inserted throughthe valve 630 and into the build chamber 628. For example, the grippermay be operated manually (e.g., via manipulation of a grip on anexterior of the system, or the gripper may be operated automatically,such as with a linear actuator. The recoater blade gripper may beconfigured to engage with and move a recoater blade housing and recoaterblade into and out of the build chamber via any suitable type ofengagement, such as a mechanical, magnetic, electrical, and/or adhesiveinterface.

In some embodiments, the recoater blade exchange chamber 632 may beremovably attachable to the enclosure around the build volume 628 via ajoint 638, such as a breakable union joint. In this manner, afterremoving a used recoater blade 618 into the recoater blade exchangechamber 632, the valve 630 may be closed and, the joint 638 may bedisconnected, and the recoater blade exchange chamber may be removedfrom the system. Subsequently, a replacement recoater blade may beloaded into the recoater blade exchange chamber, and the chamber may bereattached to the joint 638. After tightening the joint to secure theexchange chamber, the exchange chamber may be purged with inert gas toremove any oxygen and/or moisture before opening the valve 630 to insertthe replacement blade into the build volume.

The above-described embodiments of the technology described herein canbe implemented in any of numerous ways. For example, the embodiments maybe implemented using hardware, software or a combination thereof. Whenimplemented in software, the software code can be executed on anysuitable processor or collection of processors, whether provided in asingle computing device or distributed among multiple computing devices.Such processors may be implemented as integrated circuits, with one ormore processors in an integrated circuit component, includingcommercially available integrated circuit components known in the art bynames such as CPU chips, GPU chips, microprocessor, microcontroller, orco-processor. Alternatively, a processor may be implemented in customcircuitry, such as an ASIC, or semicustom circuitry resulting fromconfiguring a programmable logic device. As yet a further alternative, aprocessor may be a portion of a larger circuit or semiconductor device,whether commercially available, semi-custom or custom. As a specificexample, some commercially available microprocessors have multiple coressuch that one or a subset of those cores may constitute a processor.Though, a processor may be implemented using circuitry in any suitableformat.

Further, it should be appreciated that a computing device may beembodied in any of a number of forms, such as a rack-mounted computer, adesktop computer, a laptop computer, or a tablet computer. Additionally,a computing device may be embedded in a device not generally regarded asa computing device but with suitable processing capabilities, includinga Personal Digital Assistant (PDA), a smart phone, tablet, or any othersuitable portable or fixed electronic device.

Also, a computing device may have one or more input and output devices.These devices can be used, among other things, to present a userinterface. Examples of output devices that can be used to provide a userinterface include display screens for visual presentation of output andspeakers or other sound generating devices for audible presentation ofoutput. Examples of input devices that can be used for a user interfaceinclude keyboards, individual buttons, and pointing devices, such asmice, touch pads, and digitizing tablets. As another example, acomputing device may receive input information through speechrecognition or in other audible format.

Such computing devices may be interconnected by one or more networks inany suitable form, including as a local area network or a wide areanetwork, such as an enterprise network or the Internet. Such networksmay be based on any suitable technology and may operate according to anysuitable protocol and may include wireless networks, wired networks orfiber optic networks.

Also, the various methods or processes outlined herein may be coded assoftware that is executable on one or more processors that employ anyone of a variety of operating systems or platforms. Additionally, suchsoftware may be written using any of a number of suitable programminglanguages and/or programming or scripting tools, and also may becompiled as executable machine language code or intermediate code thatis executed on a framework or virtual machine.

In this respect, the embodiments described herein may be embodied as acomputer readable storage medium (or multiple computer readable media)(e.g., a computer memory, one or more floppy discs, compact discs (CD),optical discs, digital video disks (DVD), magnetic tapes, flashmemories, RAM, ROM, EEPROM, circuit configurations in Field ProgrammableGate Arrays or other semiconductor devices, or other tangible computerstorage medium) encoded with one or more programs that, when executed onone or more computers or other processors, perform methods thatimplement the various embodiments discussed above. As is apparent fromthe foregoing examples, a computer readable storage medium may retaininformation for a sufficient time to provide computer-executableinstructions in a non-transitory form. Such a computer readable storagemedium or media can be transportable, such that the program or programsstored thereon can be loaded onto one or more different computingdevices or other processors to implement various aspects of the presentdisclosure as discussed above. As used herein, the term“computer-readable storage medium” encompasses only a non-transitorycomputer-readable medium that can be considered to be a manufacture(i.e., article of manufacture) or a machine. Alternatively oradditionally, the disclosure may be embodied as a computer readablemedium other than a computer-readable storage medium, such as apropagating signal.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that can be employed to program a computing device or otherprocessor to implement various aspects of the present disclosure asdiscussed above. Additionally, it should be appreciated that accordingto one aspect of this embodiment, one or more computer programs thatwhen executed perform methods of the present disclosure need not resideon a single computing device or processor, but may be distributed in amodular fashion amongst a number of different computers or processors toimplement various aspects of the present disclosure.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

The embodiments described herein may be embodied as a method, of whichan example has been provided. The acts performed as part of the methodmay be ordered in any suitable way. Accordingly, embodiments may beconstructed in which acts are performed in an order different thanillustrated, which may include performing some acts simultaneously, eventhough shown as sequential acts in illustrative embodiments.

Further, some actions are described as taken by a “user.” It should beappreciated that a “user” need not be a single individual, and that insome embodiments, actions attributable to a “user” may be performed by ateam of individuals and/or an individual in combination withcomputer-assisted tools or other mechanisms.

While the present teachings have been described in conjunction withvarious embodiments and examples, it is not intended that the presentteachings be limited to such embodiments or examples. On the contrary,the present teachings encompass various alternatives, modifications, andequivalents, as will be appreciated by those of skill in the art.Accordingly, the foregoing description and drawings are by way ofexample only.

What is claimed is:
 1. A method of leveling a build surface of anadditive manufacturing system, the method comprising: detecting anorientation of a build surface; comparing the orientation of the buildsurface to a reference orientation; depositing a layer of materialhaving a non-uniform thickness onto a portion of the build surface; andfusing at least a portion of the layer of material to form at least aportion of the build surface.
 2. The method of claim 1, wherein theportion of the layer defines at least one anchor point to which amanufactured part is coupled to the build surface during an additivemanufacturing process.
 3. The method of claim 1, wherein an orientationof the build surface is substantially equal to the referenceorientation.
 4. The method of claim 1, wherein the reference orientationis a level orientation.
 5. The method of claim 1, further comprisingrepeating the steps of depositing a layer of material and fusing atleast a portion of the layer of material.
 6. The method of claim 5,wherein the fused portions of each layer are aligned.
 7. The method ofclaim 1, wherein the portion of the layer comprises substantially theentire layer.
 8. A method of locating a contact point between a recoaterblade and an obstacle on a build surface, the method comprising:translating a recoater blade in a first orientation across a buildsurface in a first pass; detecting a first contact point on the buildsurface based on a first contact between the recoater blade and anobstacle on the build surface; translating the recoater blade in asecond orientation across the build surface in a second pass; detectinga second contact point on the build surface based on a second contactbetween the recoater blade and the obstacle during the second pass; anddetermining a position of the obstacle on the build surface based on thefirst contact point and the second contact point.
 9. The method of claim8, wherein determining the position of the obstacle on the build surfacecomprises: determining a first line passing through the first contactpoint and parallel to the recoater blade when the recoater blade is inthe first orientation; determining a second line passing through thesecond contact point and parallel to the recoater blade when therecoater blade is in the second orientation; and determining anintersection point of the first line and the second line.
 10. The methodof claim 9, wherein determining the first line comprises determiningfirst positions of ends of the recoater blade when the recoater blade isin the first orientation, and wherein determining the second linecomprises determining second positions of the ends of the recoater bladewhen the recoater blade is in the second orientation.
 11. The method ofclaim 10, wherein determining the first and second positions of the endsof the recoater blade comprises reading at least one sensor associatedwith the recoater blade.
 12. The method of claim 11, wherein the atleast one sensor comprises a motor encoder and or a displacement sensor.13. The method of claim 10, wherein determining the first and secondpositions of the ends of the recoater blade comprises monitoring anamount of current delivered to one or more motors associated with therecoater blade.
 14. A method of operating a recoater of an additivemanufacturing system, the method comprising: obtaining a shape of alayer in an additive manufacturing process; determining a portion of theshape of the layer having an edge parallel to a recoater blade when therecoater blade is in a first orientation; displacing the recoater bladeacross a portion of the layer; and moving the recoater blade from thefirst orientation to a second orientation prior to the recoater bladecontacting the edge, wherein the recoater blade is not parallel to theedge when the recoater blade is in the second orientation.
 15. Themethod of claim 14, wherein the recoater blade is parallel to the layerin both the first orientation and second orientation.
 16. The method ofclaim 14, further comprising displacing the recoater blade past the edgewhile the recoater blade is in the second orientation.
 17. The method ofclaim 16, further comprising moving the recoater blade from the secondorientation to the first orientation after displacing the recoater bladepast the edge.
 18. The method of claim 16, further comprising moving therecoater blade from the second orientation to a third orientation afterdisplacing the recoater blade past the edge.
 19. The method of claim 14,wherein the recoater blade is perpendicular to a direction of movementof the recoater blade across the layer.
 20. The method of claim 14,wherein moving the recoater blade from the first orientation to thesecond orientation comprises dynamically yawing the recoater blade asthe recoater blade is displaced across the portion of the layer.